Atomizer, spray-drying apparatus, and method for manufacturing composite particles

ABSTRACT

A nozzle part dropping a slurry and a rotary disk centrifugally spraying the slurry to be dropped from the nozzle part are included. The rotary disk includes a plurality of grooves stretching in a radiation direction at least in a periphery part of a surface on which the slurry is sprayed.

TECHNICAL FIELD

The present invention relates to an atomizer centrifugally sprayingslurry, a spray-drying apparatus including the atomizer, and a methodfor manufacturing composite particles used for manufacturing anelectrode for an electrochemical device.

BACKGROUND ART

Conventionally, a method using an atomizer with a pin type rotary diskhas been known in a spray-drying granulation method, one of the methodsfor manufacturing particles. For example, Patent Literature 1 disclosesa spray part that constitutes an atomizer. The spray part includes aslurry hose discharging a slurry and a pin type rotary diskcentrifugally spraying the slurry. The pin type rotary disk hereinincludes a doughnut-shaped upper board, a planar circular-shaped lowerboard, and a plurality of dispersing pins arranged in a circumferentialdirection in an outer circumference of an upper surface of the lowerboard. The dispersing pins connect the upper board and the lower board.In a spray-drying apparatus disclosed in Patent Literature 1, the slurrydischarged from the slurry hose is dropped on the surface of the lowerboard of the rotating rotary disk. The slurry moves to the outercircumference of the surface of the lower board by centrifugal force dueto rotation of the rotary disk and is sprayed from the rotary diskthrough the dispersing pins. The sprayed slurry is then dried with hotair so as to obtain particles.

CITATION LIST Patent Literature

Patent Literature 1: JP 2006-43555 A

SUMMARY OF INVENTION Technical Problem

As mentioned above, a typical example of the conventional atomizerincludes an atomizer provided with a pin type rotary disk including anupper board, a lower board, and a plurality of pins connecting theseboards. However, the slurry dropped from a nozzle part does not spreaduniformly on a planar surface of the lower board so that an amount ofthe slurry to be sprayed may not be uniform. Furthermore, as the slurryis centrifugally sprayed from various points between the pins, forexample, from a bottom end or a top end of each pin, there is a problemthat a size of a droplet of the slurry may not be uniform. Therefore,there are problems that a particle size of particles to be manufacturedmay not be uniform and that particle size distribution may not be sharp.

Further, the lower board has a disk-like shape and the slurry iscentrifugally sprayed from an edge part of the lower board, so that someslurry may not be centrifugally sprayed from the pin type rotary diskbut fixes to a side surface part of the lower board. Similarly, someslurry may not be centrifugally sprayed from the pin type rotary diskbut fixes to, for example, the bottom end and the top end of each pin orto a back surface of the upper board. Therefore, there are problems thatthe pin type rotary disk gets clogged and that the fixing slurry peelsoff and gets mixed in granulated particles.

An object of the present invention is to provide an atomizer capable ofpreventing deviation in particle size of the granulated particles andcapable of obtaining sharp particle size distribution, a spray-dryingapparatus including the atomizer, and a method for manufacturingcomposite particles used for manufacturing an electrode for anelectrochemical device using the atomizer.

Solution to Problem

The present inventors have studied intensely and have found that theabove-mentioned object can be achieved by removing an upper board and apin from a rotary disk and forming a plurality of grooves stretching ina radiation direction at least at a periphery part of a surface of therotary disk (lower board) where slurry is sprayed, thereby completed thepresent invention.

In other words, according to the present invention, there are provided:

(1) an atomizer including a nozzle part dropping a slurry and a rotarydisk centrifugally spraying the slurry to be dropped from the nozzlepart, in which the rotary disk includes a plurality of groovesstretching in a radiation direction at least in a periphery part of asurface on which the slurry is sprayed;(2) the atomizer according to (1), in which the rotary disk has adisk-like shape and includes an annular inclined surface inclining in aradiation direction, the inclined surface being formed around a centralportion of the disk-like shape and having a predetermined angle relativeto a horizontal direction;(3) the atomizer according to (2), in which the rotary disk includes aliquid reservoir part reserving the slurry at least around a centralportion of an upper surface of the disk-like shape;(4) the atomizer according to any one of (1) to (3), in which a surfacewhich has the plurality of grooves is on an upper surface of the rotarydisk;(5) the atomizer according to any one of (1) to (3), in which a surfacewhich has the plurality of grooves is on a lower surface of the rotarydisk, and the rotary disk includes twenty or more holescircumferentially arranged and penetrating from an upper surface of therotary disk to the lower surface;(6) the atomizer according to any one of (1) to (5), in which each ofthe grooves has a width equal to or more than 50 μm and equal to or lessthan 5 mm and has a depth equal to or more than 50 μm and equal to orless than 5 mm;(7) the atomizer according to any one of (1) to (6), in which a linearvelocity of the slurry to be dropped from the nozzle part is equal to ormore than 50 m/min;(8) the atomizer according to any one of (1) to (7), in which a/b isequal to or more than 0.8, where “a” represents a width of each of thegrooves and “b” represents a pitch of adjacent grooves;(9) the atomizer according to any one of (1) to (8), in which the rotarydisk is coated with a water repellent material;(10) the atomizer according to any one of (1) to (8), in which therotary disk is coated with a water repellent material and a materialhaving higher abrasion resistance than a material used for forming therotary disk;(11) the atomizer according to (2), in which a difference in a verticaldirection between a position on which the slurry is dropped from thenozzle part and a lowest position of the inclined surface or a highestposition of the inclined surface is equal to or more than 1 mm;(12) the atomizer according to (2) or (11), in which the inclinedsurface is a curved surface;(13) the atomizer according to (3), in which the liquid reservoir partis an annular concave portion;(14) the atomizer according to any one of (1) to (13), in which theslurry is a slurry for composite particles for dry molding used formanufacturing an electrode for an electrochemical device;(15) a spray-drying apparatus including the atomizer according to anyone of (1) to (14) and a drying furnace drying the slurry centrifugallysprayed from the atomizer; and(16) a method for manufacturing composite particles using the atomizeraccording to any one of (1) to (14), the method including: a sprayingstep of centrifugally spraying a slurry for composite particles for drymolding used for manufacturing an electrode for an electrochemicaldevice; and a drying step of drying the slurry centrifugally sprayed inthe spraying step.

Advantageous Effects of Invention

According to the present invention, it is possible to provide anatomizer capable of preventing deviation in particle size of granulatedparticles and capable of obtaining sharp particle size distribution, aspray-drying apparatus including the atomizer, and a method formanufacturing composite particles used for manufacturing an electrodefor an electrochemical device using the atomizer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating a spray-drying apparatusaccording to an embodiment of the present invention.

FIG. 2 is a view illustrating a configuration of a rotary disk accordingto the embodiment of the present invention.

FIG. 3 is a view illustrating a configuration of another rotary diskaccording to the embodiment of the present invention.

FIG. 4 is a view illustrating a configuration of another rotary diskaccording to the embodiment of the present invention.

FIG. 5 is a view illustrating a configuration of another rotary diskaccording to the embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a configuration of anotherrotary disk according to the embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a configuration of anotherrotary disk according to the embodiment of the present invention.

FIG. 8 is a perspective view illustrating a configuration of anotherrotary disk according to the embodiment of the present invention.

FIG. 9 is an enlarged view illustrating a configuration of grooves ofanother rotary disk according to the embodiment of the presentinvention.

FIG. 10 is a graph illustrating number-based particle size distributionsof the rotary disk according to the embodiment and a conventional rotarydisk.

FIG. 11 is a graph illustrating volume-based particle size distributionsof the rotary disk according to the embodiment and the conventionalrotary disk.

FIG. 12 is a graph illustrating volume-based particle size distributionsof a rotary disk not coated with a water repellent ICF.

FIG. 13 is a graph illustrating volume-based particle size distributionsof a rotary disk coated with the water repellent ICF.

FIG. 14 is a view illustrating a configuration of the other rotary diskaccording to the embodiment of the present invention.

FIG. 15 is a view illustrating a configuration of a rotary diskaccording to Comparative Example 1.

FIG. 16 is a view illustrating a configuration of a rotary diskaccording to Comparative Example 2.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an atomizer according to an embodiment of the presentinvention, a spray-drying apparatus including the atomizer, and a methodfor manufacturing composite particles used for manufacturing anelectrode for an electrochemical device are described with reference todrawings. FIG. 1 is a schematic view illustrating a spray-dryingapparatus according to the embodiment of the present invention. Asillustrated in FIG. 1, a spray-drying apparatus 2 includes a dryingfurnace 4 which dries a dropped slurry with hot-air.

Above the drying furnace 4, an atomizer 6 which centrifugally sprays theslurry inside the drying furnace 4 and a slurry feeding part 8 whichfeeds the slurry to the atomizer 6 are provided. The atomizer 6 isconfigured to include a nozzle part 10, a valve driving part 12, arotary disk 14, a motor 16, and a control part 18.

The nozzle part 10 drops the slurry fed from the slurry feeding part 8on the rotary disk 14. The valve driving part 12 opens and closes avalve (not illustrated) for adjusting an amount of the slurry to bedropped from the nozzle part 10. The disk-shaped rotary disk 14 (seeFIG. 2) rotates so as to centrifugally spray the slurry to be droppedfrom the nozzle part 10 on a disk-shaped upper surface in a vicinity ofa central portion. The motor 16 rotates the rotary disk 14. The controlpart 18 controls drive of the valve driving part 12 and the motor 16 soas to control the amount of the slurry to be dropped from the nozzlepart 10 as well as a rotation speed of the rotary disk 14.

In this embodiment, the control part 18 controls the drive of the valvedriving part 12 so that a linear velocity of the slurry to be droppedfrom the nozzle part 10 becomes equal to or more than 50 m/min. Thereason is that if the linear velocity of the slurry is less than 50m/min, the slurry cannot be fed as spreading over an inclined surface 14a (see FIG. 2) of the rotary disk 14. Herein, the linear velocity of theslurry is determined by a diameter of a portion in the nozzle part 10which feeds the slurry (hereinafter referred to as a nozzle diameter)and by a flow rate of the slurry to be fed from the nozzle part 10. Notethat, the nozzle diameter and the flow rate of the slurry are preferablysmall in a case, for example, where a diameter of the rotary disk issmall, where processing performance of the rotary disk such as therotation speed is low, and where drying performance of the dryingfurnace is low. For example, the nozzle diameter is preferably equal toor less than 1.8 mm, more preferably equal to or less than 1 mm, andfurther more preferably equal to or less than 0.8 mm in a case where therotary disk 14 has a diameter of 50 mm and where the drying performance(an amount of evaporated water per unit time) of the drying furnace 4 isranging from 10 to 50 g/min.

However, when the nozzle diameter is smaller than a size of fillerincluded in the slurry, there is a possibility that the nozzle part 10gets clogged. Furthermore, when the nozzle diameter is made extremelysmall, high pressure is required in feeding the slurry from the slurryfeeding part 8, which may lead to abrade the nozzle part 10.Accordingly, the nozzle diameter is preferably equal to or more than 0.3mm. Note that, the atomizer 6 according to the embodiment includes onenozzle part 10. However, it should be noted that the atomizer 6 mayinclude a plurality of nozzle parts. In such a case, it is preferablethat each nozzle diameter is made smaller than in a case where onenozzle part is included. Herein, each nozzle diameter is adjusted sothat the slurry is fed from every nozzle at the linear velocity equal toor more than 50 m/min.

The nozzle diameter of the nozzle part 10 can be adjusted by inserting asilicon tube and the like into a tube that constitutes the nozzle part10. For example, when the tube (an existing tube) that constitutes thenozzle part 10 has an external diameter of 4 mm and an internal diameterof 3 mm. The nozzle diameter can be changed from 3 mm to 1 mm byinserting a silicon tube having an external diameter of 3 mm and aninternal diameter of 1 mm into the existing tube. Furthermore, thenozzle diameter can be changed from 1 mm to 0.5 mm by inserting asilicon tube having an external diameter of 1 mm and an internaldiameter of 0.5 mm into the silicon tube having the external diameter of3 mm and the internal diameter of 1 mm.

FIG. 2 is a view illustrating a configuration of the rotary disk 14. Asillustrated in FIG. 2, the rotary disk 14 is formed with annularinclined surfaces 14 a, 14 b in an upper surface of the rotary disk 14.Each of the inclined surfaces 14 a, 14 b inclined in a radiationdirection is formed around a central portion of the rotary disk 14 andhas a predetermined angle relative to a horizontal direction. Theinclined surface 14 a is an annular inclined and curved surfaceascending in the radiation direction from the central portion of therotary disk 14. The inclined surface 14 b is an annular inclined andcurved surface disposed in an outer circumference of the inclinedsurface 14 a and descending in the radiation direction from the centralportion of the rotary disk 14. In other words, the inclined surface 14 ais the annular surface inclined in the radiation direction and isdisposed around the central portion of the disk-like shape of the rotarydisk 14. The inclined surface 14 a further has the predetermined anglerelative to a vertical surface direction to a rotation axis of therotary disk 14 (normally, in the horizontal direction) at least from aposition where the slurry is dropped to a position where the slurry issprayed.

The vicinity of the central portion in the upper surface of the rotarydisk 14 is an annular concave portion surrounded by the inclined surface14 a and constitutes a liquid reservoir part 15 reserving the slurrydropped from the nozzle part 10. In other words, the liquid reservoirpart 15 is formed between the position in the rotary disk 14 where theslurry is dropped and grooves 20 disposed in a periphery part of therotary disk 14. The liquid reservoir part 15 may temporarily reserve theslurry which moves in an outer circumferential direction of the rotarydisk 14 due to centrifugal force. Furthermore, the liquid reservoir part15 is the annular concave portion and is formed between an annularinclined portion (the inclined surface 14 a) and the central portion ofthe rotary disk 14. Herein, the annular inclined portion has an anglegradually increasing with respect to a surface perpendicular to therotation axis of the rotary disk 14.

As illustrated in FIG. 2, in the periphery part of the upper surface ofthe rotary disk 14, that is, in an upper part of the annular inclinedsurface 14 b, a plurality of grooves 20 stretching in the radiationdirection is formed at regular intervals. Each groove 20 has a constantwidth and a constant depth. Further, a surface of the rotary disk 14 iscoated with DLC (water repellent ICF) imparted with water repellency bydoping an intrinsic carbon film (ICF) with fluorine.

The slurry dropped from the nozzle part 10 at the linear velocity equalto or more than 50 m/min is dropped on the upper surface in the vicinityof the central portion of the rotary disk 14. The slurry dropped on theupper surface in the vicinity of the central portion of the rotary disk14 and temporarily reserved in the liquid reservoir part 15 disposed inthe vicinity of the central portion of the rotary disk 14 ascends asspreading uniformly over the inclined surface 14 a by the centrifugalforce due to rotation of the rotary disk 14. The slurry ascending theinclined surface 14 a is not sprayed in the horizontal direction at aconnection part where the inclined surface 14 a and the inclined surface14 b are smoothly connected because of force in the radiation directiondue to the centrifugal force and downward force due to surface tensionof the slurry. However, the slurry passes through the grooves 20 formedin the upper part of the inclined surface 14 b and is centrifugallysprayed in a downward direction at a predetermined angle relative to thehorizontal direction as illustrated in FIG. 1.

The slurry temporarily reserved in the liquid reservoir part 15 in thevicinity of the central portion of the rotary disk 14 ascends asspreading uniformly over the inclined surface 14 a. Therefore, an amountof the slurry centrifugally sprayed from the rotary disk 14 isstabilized and thus particle size of granulated particles to bemanufactured will be stabilized. Furthermore, the inclined surface 14 bis a curved surface so that the slurry is sprayed before reaching aconnection part between a bottom part of the inclined surface 14 b and aside part of the rotary disk 14. Accordingly, it is possible to preventsome slurry from fixing to the side part 14 c of the rotary disk 14without being centrifugally sprayed from the rotary disk 14.Furthermore, the surface of the rotary disk 14 is coated with the waterrepellent ICF so that wettability of the slurry with respect to therotary disk 14 is weak, which leads to prevent the slurry from adheringto the surface of the rotary disk 14.

Herein, a difference in a vertical direction between a position on theupper surface in the vicinity of the central portion of the rotary disk14 where the slurry is dropped from the nozzle part 10 and the highestposition of the inclined surface 14 a is preferably equal to or morethan 1 mm. The reason is that if the difference is smaller than 1 mm,the slurry cannot uniformly spread over the inclined surface 14 a butbursts out from the rotary disk 14 in a form of a liquid, not a finepowder (mist), and adheres to an internal wall of the drying furnace 4before dried inside the drying furnace 4 so that the composite particlescannot be obtained.

Further, the grooves 20 control the amount of the slurry centrifugallysprayed from the rotary disk 14 as the slurry passing through thegrooves 20. In other words, since the slurry passes through theplurality of grooves 20 each having the constant width and the constantdepth, the amount of the slurry centrifugally sprayed from the rotarydisk 14 is stabilized and the particle size of the granulated particlesto be manufactured is stabilized. Note that, the grooves 20 arepreferably disposed at least in a periphery part of a surface of therotary disk 14 where the slurry is sprayed (a slurry spraying surface),that is, a surface with a separation point where the slurry is separatedfrom the rotary disk 14 so as to be sprayed. Herein, the “surface wherethe slurry is sprayed” indicates a surface, among the surfaces of therotary disk, including the separation point where the slurry isseparated from the rotary disk and made into mist (droplets). Theplurality of grooves stretching in the radial direction is formed atleast in the periphery part of such a surface and the slurry is sprayedthrough the grooves. Note that, a surface where the slurry to be droppedfrom the nozzle, that is, a surface where the slurry is brought intocontact with the rotary disk for the first time may be different fromthe surface where the slurry is sprayed. In such a case, for example,both surfaces are connected through a through hole and the like so thatthe dropped slurry passes through the through hole and moves to thesurface where the slurry is sprayed, and then the slurry is sprayedthrough the grooves.

Specifically, if the upper surface where the slurry is dropped is theslurry spraying surface, the grooves 20 are preferably disposed in theperiphery part of the upper surface. Alternatively, if a surface otherthan the upper surface where the slurry is dropped (for example, a backsurface of the upper surface where the slurry is dropped or a sidesurface of the rotary disk 14) is the slurry spraying surface, thegrooves 20 are preferably disposed in a periphery part of the surfaceother than the upper surface. Further, the grooves 20 are preferablydisposed in the periphery part and also in a position close to theposition where the slurry is sprayed within a slurry flow path rangingfrom the position where slurry is dropped to the position where theslurry is sprayed.

Further, it is possible to control the amount of the slurry to becentrifugally sprayed from the rotary disk 14 by changing the width andthe depth of each groove 20. As a result, it is possible to control theparticle size of the granulated particles to be manufactured. In otherwords, it is possible to decrease (increase) the amount of the slurry tobe centrifugally sprayed from the rotary disk 14 by decreasing(increasing) the width and the depth of each groove 20. Therefore, it ispossible to achieve decrease (increase) in the particle size of thegranulated particles to be manufactured.

Herein, each groove 20 has a width equal to or more than 50 μm and equalto or less than 5 mm, a depth equal to or more than 50 μm and equal toor less than 5 mm. Preferably, the width is equal to or more than 150 μmand equal to or less than 2 mm, the depth is equal to or more than 50 μmand equal to or less than 1 mm. More preferably, the width is equal toor more than 250 μm and equal to or less than 1 mm, and the depth isequal to or more than 300 μm and equal to or less than 1 mm. The reasonis that if each groove 20 has a width less than 50 μm and a depth lessthan 50 μm, the slurry cannot pass through the grooves 20.Alternatively, if each groove 20 has a width more than 5 mm and a depthmore than 5 mm, the amount of the slurry to be centrifugally sprayed,that is, the particle size of the granulated particles may not beuniform.

The slurry used in the spray-drying apparatus 2 may include electrodeactive materials and solvents. The slurry may also include binders,dispersing agents, electroconductive materials, and additives ifnecessary. Furthermore, the slurry herein can be widely applied toslurry which may be raw materials of the granulated particles to bemanufactured by spray-drying. Examples of such slurry include foods,pharmaceuticals, and agricultural chemicals.

In a case where the composite particles are used as electrode materialsfor lithium ion batteries, examples of the electrode active materialsfor a positive electrode include metal oxides capable of reversiblydoping and dedoping lithium ions. Examples of such metal oxides includelithium cobaltate, lithium nickelate, lithium manganate, and lithiumphosphate. Note that, the electrode active materials for a positiveelectrode mentioned in the above may be used alone, or may also be usedby mixing a plurality of kinds thereof appropriately depending on theapplication.

Note that, examples of the electrode active materials for a negativeelectrode as the counter electrode of a positive electrode for thelithium ion batteries include low crystalline carbons (amorphouscarbons) such as easily graphitizable carbon, hardly graphitizablecarbon, and pyrolytic carbon, graphite (natural graphite, artificialgraphite), alloy-base materials of tin, silicon, or the like, and oxidessuch as silicon oxides, tin oxides, and lithium titanate. Note that, theelectrode active materials for a negative electrode mentioned in theabove may be used alone, or may also be used by mixing a plurality ofkinds thereof appropriately depending on the application.

For example, a volume average particle size of the electrode activematerials for an electrode for lithium ion batteries is normally 0.1 to100 μm, preferably 0.5 to 50 μm, and more preferably 0.8 to 30 μm, forboth the positive electrode and the negative electrode.

As the solvents included in the slurry, water is preferably used, and amixed solvent of water and an organic solvent may also be used. One ofonly the organic solvents may be used alone, or several kinds thereofmay be used in combination. Examples of the organic solvents usable inthis case include alcohols, alkylketones, ethers, and amides. When anorganic solvent is used, alcohols are preferable. By using water with anorganic solvent having a boiling point lower than that of watertogether, a drying speed during drying can be accelerated. Moreover,this makes it possible to adjust viscosity and fluidity of the slurry,and to improve manufacturing efficiency.

The binders used for the composite particles are not particularlylimited as long as the binders can bind the electrode active materialsto each other. Preferable binders are dispersion type binders having aproperty of being dispersed in a solvent. Examples of the dispersiontype binders include polymer compounds such as silicon-based polymers,fluorine-containing polymers, conjugated diene-based polymers,acrylate-based polymers, polyimide, polyamide, or polyurethane,preferably include the fluorine-containing polymers, the conjugateddiene-based polymers, or the acrylate-based polymers, more preferablyinclude the conjugated diene-based polymers and the acrylate-basedpolymers.

A volume average particle size of the composite particles is within arange of normally 0.1 to 1000 μm, preferably 1 to 500 μm, morepreferably 30 to 250 μm from a viewpoint of easily obtaining anelectrode active material layer having intended thickness.

Note that, the average particle size of the composite particles is avolume average particle size measured and calculated by a laserdiffraction type particle size distribution measuring apparatus (forexample, SALD-3100, manufactured by Shimazu Corporation).

In a case of granulating composite particles for dry molding used formanufacturing an electrode for an electrochemical device with using thisspray-drying apparatus 2, first, the slurry is fed from the slurryfeeding part 8 to the nozzle part 10. The slurry is then dropped fromthe nozzle part 10 on the upper surface in the vicinity of the centralportion of the rotary disk 14. Herein, the control part 18 controls theopening and closing of the valve carried out by the valve driving part12 and adjusts the amount of the slurry to be dropped from the nozzlepart 10 so that the linear velocity of the slurry to be dropped from thenozzle part 10 becomes equal to or more than 50 m/min. Note that, amethod for feeding the slurry should not be limited to dropping. In acase of feeding the slurry to a lower surface of the rotary disk 14, theslurry may be fed as making the nozzle close to the lower surface of therotary disk 14. Furthermore, by reducing the diameter of the nozzlewhich feeds the slurry, it is possible to uniform intermittent liquidfeed, which leads to obtain the composite particles with uniformparticle size. The slurry fed herein may also be subjected toatomization by the nozzle part 10 and fed as fine droplets. Further, thecontrol part 18 also controls the rotation of the rotary disk 14 carriedout by the motor 16 and adjusts the rotation speed of the rotary disk14. The rotation speed is normally 1,000 to 90,000 rpm.

Next, the slurry dropped on the upper surface in the vicinity of thecentral portion of the rotary disk 14 is centrifugally sprayed by thecentrifugal force due to the rotation of the rotary disk 14. At thistime, the slurry is temporarily reserved in the liquid reservoir part 15in the vicinity of the central portion of the rotary disk 14. The slurrythen ascends the inclined surface 14 a by the centrifugal force due tothe rotation of the rotary disk 14. Then, the slurry ascending theinclined surface 14 a passes through the grooves 20 formed in the upperpart of the inclined surface 14 b and is centrifugally sprayed in thedownward direction at the predetermined angle relative to the horizontaldirection by the centrifugal force due to the rotation of the rotarydisk 14.

In other words, the slurry dropped on the rotary disk 14 is affected bythe centrifugal force due to the rotation of the rotary disk 14 andmoves in the outer circumferential direction of the rotary disk 14. Atthis time, the slurry is pressed against the inclined surface 14 a bythe centrifugal force so that the slurry easily and uniformly spreadsthroughout the inclined surface. Therefore, when the slurry reaches thegrooves 20 in the periphery part of the rotary disk 14, each groove isequally fed with the slurry. Since the slurry is uniformly sprayed inthe circumferential direction through each groove, the droplets of theslurry are uniform in a size and a shape. Furthermore, the slurrydropped on the rotary disk 14 can spread annually by being temporarilyreserved in the liquid reservoir part 15. Therefore, the slurry movingfrom the liquid reservoir part 15 to an outer circumferential part ofthe rotary disk 14 can be uniformly spread over the surface of therotary disk 14 in the whole direction.

Note that, if the inclined surface 14 a is absent, it may be difficultto completely and uniformly spread the dropped slurry over a disksurface depending on a concentration or a dropping amount of the slurry,rotation speed of the disk, and the like. Furthermore, buoyancy mayoccur in the vertical direction with respect to the disk surface so thatsome slurry may not be fed to the grooves 20. Further, if the liquidreservoir part 15 is absent, the dropped slurry is affected by thecentrifugal force and spreads in the outer circumferential directionbefore spreading annually also depending on a concentration or adropping amount of the slurry, rotation speed of the disk, and the like.As a result, the slurry cannot spread uniformly in the whole directionof the rotary disk 14 but is sprayed only from a partial limiteddirection.

Accordingly, even though there is the inclined surface 14 a, if theangle thereof is small or if the dropping amount of the slurry is large,the inclined surface 14 a alone cannot spread the slurry in the wholedirection depending on a concentration of the slurry, rotation speed ofthe disk, and the like. Therefore, an effect of forming uniform dropletsmay decrease. Furthermore, if the slurry reaches the grooves 20 withoutbeing reserved in the liquid reservoir part 15, the slurry may be fed asexceeding capacity of the grooves 20 depending on a dropping amount. Asa result, the slurry may overflow the grooves 20, which decreases theuniforming effect of the droplets.

Next, the droplets of the slurry centrifugally sprayed from the rotarydisk 14 are dried by hot air fed inside the drying furnace 4. By dryingthe droplets of the slurry, the granulated particles, that is, thecomposite particles for dry molding used for manufacturing an electrodefor an electrochemical device are manufactured.

According to the atomizer 6 of the present embodiment, the annularinclined surface 14 a inclined in the radiation direction is formed onthe upper surface of the rotary disk 14. Therefore, the slurry istemporarily reserved in the vicinity of the central portion of therotary disk 14 and then ascends the periphery part as spreadinguniformly. Furthermore, since the plurality of grooves 20 stretching inthe radiation direction is formed at the regular intervals in theperiphery part of the rotary disk 14, that is, in the upper part of theinclined surface 14 b, it is possible to prevent deviation in the amountof the slurry centrifugally sprayed from the rotary disk 14. Since theinclined and curved surface 14 b is formed in the upper surface of therotary disk 14, the slurry is sprayed before reaching the connectionpart of the bottom part of the inclined surface 14 b and the side partof the rotary disk 14. Accordingly, it is possible to prevent someslurry from fixing to the side part 14 c of the rotary disk 14 withoutbeing centrifugally sprayed from the rotary disk 14.

Further, different from a conventional pin type rotary disk, the rotarydisk 14 only includes a lower board, but not include an upper board anda pin. Therefore, there is no possibility that some slurry fixes to theupper board or the pin without being centrifugally sprayed from therotary disk 14. As a result, it is possible to prevent clogging due tothe fixation and to prevent the slurry which fixes to and peels off fromthe upper board or the pin from getting mixed into the granulatedparticles.

Further, in a case of using a conventional rotary disk such as the pintype rotary disk and rotating the conventional rotary disk at highspeed, the slurry dropped toward the lower board strikes against thelower board and bounces. Therefore, in the absence of the pin or theupper board, coarse droplets are discharged as it is into a drying towerso that the droplets cannot be sufficiently dried. Accordingly, in theconventional rotary disk such as the pin type rotary disk, the upperboard and the pin are provided so as to prevent the bounced droplets ofthe slurry from being discharged as it is into the drying tower.However, in such a case, the coarse droplets intermittently adhere tothe upper board, the pin, and near the nozzle which feeds liquid. Due tosuch adhesion, fixation is generated, so that there are many cases wherecontinuous operation cannot be carried out. Therefore, in order toprevent such a problem, it is necessary to adjust viscosity of theslurry.

However, according to the present embodiment, the linear velocity of theslurry to be dropped from the nozzle part 10 is controlled to be equalto or more than 50 m/min so that even though the rotary disk 14 isrotated at high speed, the slurry will not bounce and the slurry can befed continuously as spreading over the inclined surface 14 a of therotary disk 14. Therefore, there is no need to provide the upper boardor the pin. Moreover, regardless of the viscosity of the slurry, it ispossible to prevent the slurry from fixing to the nozzle part 10 orrotary disk 14. Furthermore, since the slurry can be fed as spreadingover the inclined surface 14 a, it is possible to decrease spraying thecoarse droplets. As a result, it is possible to improve a yield of thecomposite particles to be manufactured and to obtain sharp particle sizedistribution.

Furthermore, the surface of the rotary disk 14 is coated with the waterrepellent ICF so that it is possible to improve water repellency andabrasion resistance and to prevent the slurry from fixing to the rotarydisk 14. Therefore, even though the spray-drying apparatus 2 is operatedfor a long time, it is possible to continuously obtain the sharpparticle size distribution.

In addition, the slurry ascending the inclined surface 14 a and passingthrough the grooves 20 is centrifugally sprayed in the downwarddirection at the predetermined angle relative to the horizontaldirection. Consequently, compared to the conventional art in which thedroplets of the slurry are centrifugally sprayed in the horizontaldirection, a distance till the droplets of the slurry reaches theinternal wall of the drying furnace 4 becomes long so that time ofdrying the droplets of the slurry becomes long. Therefore, in a case ofusing the drying furnace 4 having a furnace size identical to that of aconventional spray-drying apparatus, it is possible to manufactureparticles having a particle size larger than those manufactured by theconventional spray-drying apparatus. Furthermore, when manufacturingparticles having a particle size identical to those manufactured by theconventional apparatus, it is possible to decrease the furnace size ofthe drying furnace and to achieve downsizing of the spray-dryingapparatus.

According to the atomizer 6 of the present embodiment, the liquidreservoir part 15 reserving the slurry is included around the centralportion of the rotary disk 14. The slurry is temporarily reserved in theliquid reservoir part 15 of the rotary disk 14 and ascends as uniformlyspreading over the inclined surface 14 a. As a result, it is possible toprevent deviation in the amount of the slurry centrifugally sprayed fromthe rotary disk 14. Further, the slurry ascends as uniformly spreadingover the inclined surface 14 a so that the particle size of thegranulated particles to be manufactured may not be easily affected bychanges in the amount of the slurry to be dropped from the nozzle part10. Therefore, it is possible to prevent deviation in the particle sizeof the granulated particles to be manufactured.

Further, according to the spray-drying apparatus 2 and the method formanufacturing the granulated particles using the spray-drying apparatus2, because the atomizer 6 is included, it is possible to preventdeviation in the particle size of the composite particles to bemanufactured and to obtain the sharp particle size distribution.

Note that, in the above-mentioned embodiment, the rotary disk 14illustrated in FIG. 2 has been described as an example. However, thefollowing rotary disks are also applicable in place of the rotary disk14. That is, a rotary disk 30, a rotary disk 32, a rotary disk 37, arotary disk 42, and a rotary disk 50 respectively illustrated in FIG. 3,FIG. 4, FIG. 5, FIG. 7, and FIG. 14.

As illustrated in FIG. 3, the rotary disk 30 has a disk-like shape andis formed with an annular inclined surface 30 a in an upper surface ofthe rotary disk 30. The inclined surface 30 a inclined in a radiationdirection is formed around a central portion of the rotary disk 30 andhas a predetermined angle relative to a horizontal direction. Theinclined surface 30 a is an annular inclined and curved surfaceascending in the radiation direction from the central portion of therotary disk 30. In other words, a part around the central portion in theupper surface of the rotary disk 30 is an annular concave portionsurrounded by the inclined surface 30 a and constitutes a liquidreservoir part 32 reserving the slurry dropped from the nozzle part 10.Further, in a periphery part of the inclined surface 30 a, a pluralityof grooves 34 stretching in the radiation direction is formed at regularintervals. Each groove 34 has a constant width and a constant depth assimilar to the grooves 20. Further, a surface of the rotary disk 30 iscoated with the water repellent ICF.

In a case of using the rotary disk 30, the slurry dropped on the uppersurface in a vicinity of the central portion of the rotary disk 30 andtemporarily reserved in the liquid reservoir part 32 of the rotary disk30 ascends the inclined surface 30 a by centrifugal force due torotation of the rotary disk 30. The slurry ascending the inclinedsurface 30 a passes through the grooves 34 formed in the periphery partof the inclined surface 30 a. The slurry is then centrifugally sprayedby the centrifugal force due to the rotation of the rotary disk 30 in anupward direction at a predetermined angle relative to the horizontaldirection.

The slurry temporarily reserved in the liquid reservoir part 32 of therotary disk 30 ascends as uniformly spreading over the inclined surface30 a and is centrifugally sprayed through the grooves 34 from theperiphery part of the inclined surface 30 a. Therefore, an amount of theslurry centrifugally sprayed from the rotary disk 30 is stabilized,which leads to stabilize the particle size of the granulated particlesto be manufactured in the spray-drying apparatus 2.

Further, the slurry temporarily reserved in the liquid reservoir part 32of the rotary disk 30 ascends as uniformly spreading over the inclinedsurface 30 a. Therefore, it is possible to control the particle size ofthe granulated particles by adjusting a height of the inclined surface30 a that constitutes the liquid reservoir part 32. In other words,heightening the inclined surface 30 a decreases the size of the dropletsof the slurry centrifugally sprayed from the rotary disk 30, which leadsto achieve decrease in the particle size of the granulated particles tobe manufactured. Further, even though the amount of the slurry to bedropped from nozzle part 10 is decreased, the slurry uniformly spreadsover the inclined surface 30 a. Therefore, it is possible to manufacturethe granulated particles with small particle size. Furthermore, theslurry is centrifugally sprayed in the upward direction with thepredetermined angle relative to the horizontal direction. Therefore, thedistance till the slurry reaches the internal wall of the drying furnace4 can be made long and the time of drying the droplets of the slurry canbe made long.

Herein, a difference in the vertical direction between a position in theupper surface of the rotary disk 30 where the slurry is dropped from thenozzle part 10 and the highest position of the inclined surface 30 a ispreferably equal to or more than 1 mm. The reason is that if thedifference is smaller than 1 mm, the slurry cannot uniformly spread overthe inclined surface 30 a but bursts out from rotary disk 30 in a formof a liquid, not a fine powder (mist), and adheres to the internal wallof the drying furnace 4 before dried inside the drying furnace 4 so thatthe composite particles cannot be obtained.

As illustrated in FIG. 4, the rotary disk 32 has a disk-like shape andis formed with an annular inclined surface 32 a in an upper surface ofthe rotary disk 32. The inclined surface 32 a inclined in a radiationdirection is formed around a central portion of the rotary disk 32 andhas a predetermined angle relative to a horizontal direction. Theinclined surface 32 a is an annular inclined and curved surfacedescending from the central portion of the rotary disk 32 in theradiation direction. Further, in a periphery part of the inclinedsurface 32 a, a plurality of grooves 36 stretching in the radiationdirection is formed at regular intervals. Each groove 36 has a constantwidth and a constant depth as similar to the grooves 20. Further, asurface of the rotary disk 32 is coated with the water repellent ICF.

When the rotary disk 32 is provided, the slurry dropped on the uppersurface in a vicinity of the central portion of the rotary disk 32descends the inclined surface 32 a by centrifugal force due to rotationof the rotary disk 32. The slurry descending the inclined surface 32 apasses through the grooves 36 formed in the periphery part of theinclined surface 32 a and is centrifugally sprayed in the horizontaldirection or in a downward direction at a predetermined angle relativeto the horizontal direction by the centrifugal force due to the rotationof the rotary disk 32. The slurry descends as uniformly spreading overthe inclined surface 32 a and is centrifugally sprayed through thegrooves 36 from the periphery part of the inclined surface 32 a.Therefore, an amount of the slurry centrifugally sprayed from the rotarydisk 32 is stabilized, which leads to stabilize the particle size of thegranulated particles to be manufactured in the spray-drying apparatus 2.

Herein, a difference in a vertical direction between a position in theupper surface of the rotary disk 32 where the slurry is dropped from thenozzle part 10 and the lowest position of the inclined surface 32 a ispreferably equal to or more than 1 mm. The reason is that when thedifference is equal to or more than 1 mm, the slurry descends asuniformly spreading over the inclined surface 32 a by force in theradiation direction due to the centrifugal force and by force in thedownward direction due to gravity of the slurry. However, if thedifference is smaller than 1 mm, the slurry descends without uniformlyspreading over the inclined surface 32 a but bursts out from the rotarydisk 32 in a form of a liquid, not a fine powder (mist), and adheres tothe internal wall of the drying furnace 4 before dried inside the dryingfurnace 4 so that the composite particles cannot be obtained.

As illustrated in FIG. 5, the rotary disk 37 has a disk-like shape andis formed with holes 38 in an upper surface of the rotary disk 37. Eachhole 38 penetrates the rotary disk 37 from the upper surface to a backsurface thereof. As illustrated in a cross-sectional view in the FIG. 6,a conically inclined surface 39 is formed in a bottom part of the holes38. Further, in a periphery part of the inclined surface 39, a pluralityof grooves 40 stretching in a radiation direction is formed at regularintervals. Each groove 40 has a constant width and a constant depth assimilar to the grooves 20. Further, a surface of the rotary disk 37 iscoated with the water repellent ICF.

When the rotary disk 37 is provided, the slurry dropped on the uppersurface 37 a in a vicinity of a central portion of the rotary disk 37passes through the holes 38 by centrifugal force due to the rotation ofthe rotary disk 37 and gravity, flows into a back surface 37 b of theupper surface 37 a in the vicinity of the central portion, and descendsthe inclined surface 39. The slurry descending the inclined surface 39passes through the grooves 40 formed in the periphery part of theinclined surface 39 and is centrifugally sprayed in a horizontaldirection or in a downward direction at a predetermined angle relativeto the horizontal direction by the centrifugal force due to rotation ofthe rotary disk 37. The slurry descends as uniformly spreading over theinclined surface 39 and is centrifugally sprayed through the grooves 40from the periphery part of the inclined surface 39. Therefore, an amountof the slurry centrifugally sprayed from the rotary disk 37 isstabilized, which leads to stabilize the particle size of the granulatedparticles to be manufactured in the spray-drying apparatus 2.

The rotary disk 42 has a conically trapezoidal shape as illustrated in across-sectional view of the FIG. 7. A surface of the rotary disk 42 iscoated with the water repellent ICF. Further, in an upper surface of therotary disk 42, an annular drop surface 42 a is formed around a centralportion of the rotary disk 42. FIG. 8 is a perspective view illustratinga configuration of the rotary disk 42 seen from a downward direction (adirection to see a back surface 42 b). As illustrated in FIG. 7 and FIG.8, thirty-six holes 44 are circumferentially arranged in the dropsurface 42 a of the rotary disk 42. Each hole 44 penetrates the rotarydisk 42 from the drop surface 42 a to the back surface 42 b.

Herein, the thirty-six holes 44 are formed in the rotary disk 42.However, note that the holes formed in the rotary disk are normallytwenty or more, and preferably twenty-four or more, and more preferablythirty or more. The reason is that if the number of the holes is lessthan 20, the slurry passing through the holes cannot spread uniformlyover a spraying surface 42 c (described below) of the rotary disk 42.

The slurry dropped on the drop surface 42 a spreads uniformly over thedrop surface 42 a and passes through the holes 44. Note that, a size ofeach hole may not affect the yield of the composite particles to bemanufactured by the spray-drying apparatus 2 and the particle sizedistribution. However, the size of each hole is preferably made small inorder to maintain intensity of the rotary disk rotating at high speed.However, it should be noted that the size of each hole is preferablymade at least equal to or more than 0.5 mm, more preferably equal to ormore than 1 mm in order to prevent coagulated materials or coarseparticles from clogging in the holes.

The annular back surface 42 b and the conically inclined sprayingsurface 42 c spraying the slurry are formed on a lower surface of therotary disk 42. The back surface 42 b is the annular surface parallel toa horizontal direction and is formed around a central bottom part of therotary disk 42. The spraying surface 42 c is the annular inclinedsurface disposed in an outer circumference of the back surface 42 b anddescending in a radiation direction from a periphery part of the backsurface 42 b.

Further, in a periphery part of the spraying surface 42 c, a pluralityof grooves 46 is formed in the radiation direction at regular intervals.Each groove 46 has a constant width and a constant depth as similar tothe grooves 20. FIG. 9 is an enlarged sectional view illustrating thegrooves 46. As illustrated in FIG. 9, the grooves 46 are formed so thateach of adjacent grooves 46 is formed with no gap or with minimum gap.Specifically, the grooves 46 are formed so that a/b becomes equal to ormore than 0.8, preferably equal to or more than 0.9, more preferablyequal to or more than 0.95, where “a” is a width of each groove 46 and“b” is a pitch between the adjacent grooves 46. Therefore, the slurryuniformly spreading over the spraying surface 42 c certainly passesthrough the grooves 46. As the whole slurry passing through the grooves46, the size of the droplets of the slurry sprayed from the rotary disk42 is stabilized. Accordingly, it is possible to stabilize the particlesize of the granulated particles to be manufactured and to obtain thesharp particle size distribution.

When the rotary disk 42 is provided, the slurry dropped on the dropsurface 42 a of the rotary disk 42 passes through the holes 44 bycentrifugal force due to rotation of the rotary disk 42 and gravity,flows into the back surface 42 b, and descends the spraying surface 42c. The slurry descending the spraying surface 42 c passes through thegrooves 46 formed in the periphery part of the spraying surface 42 c andis centrifugally sprayed in the horizontal direction or in a downwarddirection at a predetermined angle relative to the horizontal directionby the centrifugal force due to the rotation of the rotary disk 42. Theslurry descends as uniformly spreading over the spraying surface 42 cand is centrifugally sprayed through the grooves 46 from the peripherypart of the spraying surface 42 c. Therefore, an amount of the slurrycentrifugally sprayed from the rotary disk 42 is stabilized, which leadsto stabilize the particle size of the granulated particles to bemanufactured in the spray-drying apparatus 2.

FIG. 10 is a graph illustrating number-based particle size distributionsten minutes after manufacturing the granulated particles, with therotation speed of the rotary disk of 14,000 rpm, (1) by the spray-dryingapparatus 2 including the rotary disk 42 and the nozzle having thenozzle diameter of 0.5 mm, (2) by the spray-drying apparatus 2 includingthe rotary disk 42 and the nozzle having the nozzle diameter of 3 mm,and (3) by the spray-drying apparatus 2 including the conventional pintype disk and the nozzle having the nozzle diameter of 3 mm. FIG. 11 isa graph illustrating volume-based particle size distributions tenminutes after manufacturing the granulated particles with the sameconditions as described in FIG. 10. As illustrated in the graphs (2) and(3) of FIG. 10 and FIG. 11, the sharp particle size distribution can beobtained by manufacturing the granulated particles with the rotary disk42 rather than manufacturing the granulated particles with theconventional pin type disk. Further, as illustrated in the graphs (1)and (2) of FIG. 10 and FIG. 11, the sharp particle size distribution canbe obtained by manufacturing the granulated particles with dropping theslurry from the nozzle having the nozzle diameter of 0.5 mm rather thanmanufacturing the granulated particles with dropping the slurry from thenozzle having the nozzle diameter of 3 mm.

Further, FIG. 12 is a graph illustrating (1) a volume-based particlesize distribution ten minutes after, (2) a volume-based particle sizedistribution twenty minutes after, and (3) a volume-based particle sizedistribution thirty minutes after manufacturing the granulated particlesby the spray-drying apparatus 2 including a rotary disk having aconfiguration similar to that of the rotary disk 42 except that it isnot coated with the water repellent ICF (rotation speed of the rotarydisk: 14,000 rpm). Further, FIG. 13 is a graph illustrating (1) avolume-based particle size distribution ten minutes after, (2) avolume-based particle size distribution twenty minutes after, and (3) avolume-based particle size distribution thirty minutes aftermanufacturing the granulated particles by the spray-drying apparatus 2including the rotary disk 42 (the rotary disk coated with the waterrepellent ICF) (the rotation speed of the rotary disk: 14,000 rpm). Asillustrated in the graphs in FIG. 12 and FIG. 13, the sharp particlesize distribution can be continuously obtained by manufacturing thegranulated particles using the rotary disk coated with the waterrepellent ICF rather than manufacturing the granulated particles usingthe rotary disk not coated with the water repellent ICF. In other words,the sharp particle size distribution can be continuously obtained bycoating the rotary disk with the water repellent ICF and improving waterrepellency and abrasion resistance of the rotary disk, even though thespray-drying apparatus 2 is operated for a long time.

As illustrated in FIG. 14, the rotary disk 50 has a flat disk-likeshape. In a periphery part of an upper surface 50 a of the rotary disk50, a plurality of grooves 52 stretching in a radiation direction isformed at regular intervals. Each groove 52 has a constant width and aconstant depth as similar to the grooves 20. Further, a surface of therotary disk 50 is coated with the water repellent ICF.

When the rotary disk 50 is provided, the slurry dropped on the uppersurface in a vicinity of a central portion of the rotary disk 50 movestoward a periphery part of the upper surface 50 a of the rotary disk 50by centrifugal force due to rotation of the rotary disk 50. The slurrythen passes through the grooves 52 formed in the periphery part and iscentrifugally sprayed in a horizontal direction or in a downwarddirection at a predetermined angle relative to the horizontal directionby the centrifugal force due to the rotation of the rotary disk 50. Asthe slurry is centrifugally sprayed through the grooves 52, an amount ofthe slurry centrifugally sprayed from the rotary disk 50 is stabilized,which leads to stabilize the particle size of the granulated particlesto be manufactured in the spray-drying apparatus 2.

Further, in the above-mentioned embodiment, the rotary disks 14, 30, 32,37, 42, 50 respectively formed with the plurality of grooves 20, 34, 36,40, 46, 52 in each periphery part of the surfaces 14 a, 30 a, 32 a, 39,42 c, 50 a where the slurry flows have been described as examples.However, it is possible to adopt a rotary disk formed with a pluralityof grooves at regular intervals stretching in a radiation direction atleast in a periphery part of a surface where the slurry flows, forexample, a part other than the periphery part as well as in theperiphery part.

Further, in the above-mentioned embodiment, the rotary disk 14 formedwith the grooves 20 in the upper part of the inclined surface 14 b (seeFIG. 2) has been described as an example. However, it is possible toadopt a rotary disk formed with grooves in a periphery part of a surfaceother than the upper part of the inclined surface 14 b, for example, inthe bottom part or upper part of the inclined surface 14 a, or in theconnection part between the inclined surface 14 a and the inclinedsurface 14 b.

Further, in the above-mentioned embodiment, the surface of the rotarydisk is coated with the water repellent ICF. However, it is possible tostably obtain uniform particles even under a long time of operation bypolishing, plating, and coating the surface of the rotary disk. A methodfor polishing should not be limited. Examples of the method includebuffing, grinding polishing, electrolytic polishing, and chemicalpolishing. Polishing makes each surface of the disk flat and smooth andprevents contamination. A preferable example of plating includes platingwith materials (for example, alumite, chrome, and nickel) havingabrasion resistance higher than materials (for example, aluminum)forming the rotary disk from a viewpoint that enhancing the hardness ofthe surface leads to prevent the abrasion. For example, it is preferableto plate a surface of the rotary disk with composite plating in whichpolytetrafluoroethylene (PTFE) is co-deposited in an electroless nickelfilm. Not only the water repellency, the mold release property, theslipping property, and the like which are the properties of the PTFE areimproved but also the hardness of the film and the abrasion resistancecan be improved with inclusion of the nickel. Further, by plating therotary disk with the electroless nickel, a surface of the rotary diskcan be coated without burying the grooves of the rotary disk.

Further, it is possible to prevent contamination by coating the rotarydisk with water repellent coats or hydrophilic coats. For example, bycoating the surface of the rotary disk with a mold release agent havingthe water repellency such as the PTFE and the like, the wettability ofthe slurry with respect to the rotary disk can be diminished so that theslurry can be prevented from fixing to the rotary disk. Furthermore,coating with the diamond-like carbon (DLC) can prevent the abrasion. Insuch manners, by coating the surface of the rotary disk with membershaving the water repellency, abrasion resistance, and the like, it ispossible to prevent the slurry from fixing to the rotary disk and tocontinuously obtain the sharp particle size distribution even throughthe spray-drying apparatus is operated for a long time. Further, evenunder repetitive use of the rotary disk, physical properties of thegranulated particles to be obtained are highly reproducible. Inaddition, it is possible to prevent foreign materials from getting mixedinto the granulated particles due to the abrasion.

EXAMPLES Example 1

97.5 parts of artificial graphite (average particle size: 24.5 μm,graphite interlayer distance (interplanar spacing (d value) of (002)plane by an X-ray diffraction method): 0.354 nm) as a negative electrodeactive material, 1.5 parts of the particulate binder resin in terms ofsolid content, and 0.7 parts of 1.0% aqueous solution ofcarboxymethylcellulose (BSH-12, manufactured by DKS Co. Ltd.) in termsof solid content as a water-soluble polymer were mixed. In addition,ion-exchanged water was added to the mixture so that a solid contentconcentration would be 35 wt. %. Thereafter, the resultant was mixed anddispersed, thereby obtaining the slurry for the composite particles.

The above-mentioned slurry for the composite particles (with the solidcontent concentration of 35%) is fed to a spray dryer (manufactured byOhkawara Kakohki Co., Ltd.) by using the following disk as a rotarydisk. That is, a doughnut-shaped disk as illustrated in FIG. 2 (adiameter of 50 mm, and a difference between a position on an uppersurface in a vicinity of a central portion and the highest position ofan inclined surface is 4 mm in a vertical direction) and includinggrooves (120 grooves with a width of 0.51 mm and a depth of 0.61 mm).The slurry was fed at 20 mL/min, with setting rotation speed of 15,000rpm, hot air temperature of 150° C., and temperature of a particlerecovery exit of 90° C. so as to carry out spray-drying granulation,thereby obtaining the composite particles.

The average particle size of the composite particles was measured by adry laser diffraction/scattering type particle size distributionmeasuring apparatus (Microtrac MT-3200II, manufactured by Nikkiso Co.,Ltd.). At this time, a value of (D90/D10) was written down on Table 1,where a cumulative 10% size in terms of volume was represented by D10size and a cumulative 90% size in terms of volume was represented by D90size.

Example 2

The composite particles were manufactured in the same manner as inExample 1 except for using a disk having a shape as illustrated in FIG.3 (a diameter of 50 mm, and a difference between a position on an uppersurface in a vicinity of a central portion and the highest position ofan inclined surface is 3 mm in a vertical direction) and includinggrooves (120 grooves with a width of 0.39 mm and a depth of 0.48 mm) inplace of the disk used in Example 1. A value (D90/D10) of the obtainedcomposite particles was written down on the Table 1.

Example 3

In place of the disk used in Example 1, a disk as illustrated in FIG. 7(an external diameter of 50 mm, thirty-six holes, and grooves eachhaving a width of 0.3 mm and a depth of 0.2 mm) not coated with thewater repellent ICF was used. A nozzle having a nozzle diameter(internal diameter) of 0.5 mm was used to feed liquid to the disk androtation speed was set at 14,000 rpm. The composite particles weremanufactured under a condition similar to that of Example 1 except forthe above-mentioned conditions. Note that, the linear velocity herein ofthe nozzle part feeding the liquid was 102 m/min. Sampling was carriedout ten minutes after starting operation. A value (D90/D10) of theobtained composite particles was 1.99.

Example 4

The composite particles were manufactured in the same manner as inExample 3 except that the disk used in Example 3 was coated with thewater repellent ICF (manufactured by Nanotec Corporation) having athickness of 1 μm. Sampling was carried out three times on the obtainedcomposite particles at 20-minute intervals. Then, the particle sizedistribution of each time was measured. Values (D90/D10) of the obtainedcomposite particles were written down on the Table 2.

Comparative Example 1

The composite particles were manufactured in the same manner as inExample 1 except for using a disk as illustrated in FIG. 15 having aplanar circular shape (a diameter of 50 mm) in place of the disk used inExample 1. Herein, particles with a fine particle size could not beobtained.

Comparative Example 2

The composite particles were manufactured in the same manner as inExample 1 except for using, in place of the disk used in Example 1, adoughnut-shaped disk as illustrated in FIG. 16 (a diameter of 50 mm, anda difference between a position on an upper surface in a vicinity of acentral portion and the highest position of an inclined surface is 4 mmin a vertical direction) and including no grooves. A value (D90/D10) ofthe obtained composite particles was written down on the Table 1.

Comparative Example 3

The composite particles were manufactured in the same manner as inExample 1 except that a pin type disk (a diameter of 50 mm) was used inplace of the disk used in Example 1. A value (D90/D10) of the obtainedcomposite particles was written down on the Table 1.

TABLE 1 (D90/D10) in terms of volume Example 1 1.98 Example 2 1.83Example 3 1.99 Comparative Example 1 Could not granulated ComparativeExample 2 2.20 Comparative Example 3 2.26

Example 4

TABLE 2 (D90/D10) in terms of volume After 20 minutes 2.00 After 40minutes 2.06 After 60 minutes 2.09

As illustrated in the above-mentioned Examples, (D90/D10) of thecomposite particles used for manufacturing an electrode for anelectrochemical device which are obtained by using the disk of thepresent invention is lower than that of composite particles which areobtained by using the conventional pin type disk. Therefore, it can besaid that the particle size distribution obtained by using the disk ofthe present invention is sharp.

1. An atomizer comprising: a nozzle part dropping a slurry; and a rotarydisk centrifugally spraying the slurry to be dropped from the nozzlepart, wherein the rotary disk includes a plurality of grooves stretchingin a radiation direction at least in a periphery part of a surface onwhich the slurry is sprayed.
 2. The atomizer according to claim 1,wherein the rotary disk has a disk-like shape and includes an annularinclined surface inclined in a radiation direction, the inclined surfacebeing formed around a central portion of the disk-like shape and havinga predetermined angle relative to a horizontal direction.
 3. Theatomizer according to claim 2, wherein the rotary disk includes a liquidreservoir part reserving the slurry at least around a central portion ofan upper surface of the disk-like shape.
 4. The atomizer according toclaim 1, wherein a surface which has the plurality of grooves is on anupper surface of the rotary disk.
 5. The atomizer according to claim 1,wherein a surface which has the plurality of grooves is on a lowersurface of the rotary disk, and the rotary disk includes twenty or moreholes circumferentially arranged and penetrating from an upper surfaceof the rotary disk to the lower surface.
 6. The atomizer according toclaim 1, wherein each of the grooves has a width equal to or more than50 μm and equal to or less than 5 mm and has a depth equal to or morethan 50 μm and equal to or less than 5 mm.
 7. The atomizer according toclaim 1, wherein a linear velocity of the slurry to be dropped from thenozzle part is equal to or more than 50 m/min.
 8. The atomizer accordingto claim 1, wherein a/b is equal to or more than 0.8, where “a”represents a width of each of the grooves and “b” represents a pitch ofadjacent grooves.
 9. The atomizer according to claim 1, wherein therotary disk is coated with a water repellent material.
 10. The atomizeraccording to claim 1, wherein the rotary disk is coated with a waterrepellent material and a material having higher abrasion resistance thana material used for forming the rotary disk.
 11. The atomizer accordingto claim 2, wherein a difference in a vertical direction between aposition on which the slurry is dropped from the nozzle part and alowest position of the inclined surface or a highest position of theinclined surface is equal to or more than 1 mm.
 12. The atomizeraccording to claim 2, wherein the inclined surface is a curved surface.13. The atomizer according to claim 3, wherein the liquid reservoir partis an annular concave portion.
 14. The atomizer according to claim 1,wherein the slurry is a slurry for composite particles for dry moldingused for manufacturing an electrode for an electrochemical device.
 15. Aspray-drying apparatus comprising: the atomizer according to claim 1;and a drying furnace drying the slurry centrifugally sprayed from theatomizer.
 16. A method for manufacturing composite particles using theatomizer according to claim 1, the method comprising: a spraying step ofcentrifugally spraying a slurry for composite particles for dry moldingused for manufacturing an electrode for an electrochemical device; and adrying step of drying the slurry centrifugally sprayed in the sprayingstep.